Specimen Information

Most patients achieve a satisfactory therapeutic response in the serum concentration range of 5-12 µg/mL (23-55 µmol/L)Concentrations above 12 µg/mL (55 µmol/L) usually produce side effects.Because of patient-to-patient differences in metabolic activity and intensity of epileptic seizures, some patients may require serum levels outside of this range for effective therapeutic control. Therefore, the expected range is provided only as a guide, and individual patient results should be interpreted in light of other clinical signs and symptoms.Critical High Value:≥ 12.1 ug/mL

Methodology

Enzyme Immunoassay (EIA)

Clinical Significance

To evaluate adequacy of primidone therapyPrimidone belongs to the group of medicines called anticonvulsants. It is used in the treatment of epilepsy to manage certain types of seizures. Primidone may be used alone or in combination with other anticonvulsants. It acts by controlling nerve impulses in the brain.Monitoring primidone concentrations in serum is an effective means of ensuring adequate therapy for several reasons: - Serum primidone concentrations correlate better with pharmacologic activity than does dosage. - Patients taking the same dosage of primidone show considerable variation in primidone serum concentrations because of individual differences in absorption, metabolism, disease states, and compliance. Serum level monitoring helps physicians individualize dosage regimens. - Primidone is sage and effective only in a narrow range of serum concentrations.The presence of primidone’s two active metabolites, phenobarbital and phenylehtylmalodiamide (PEMA), complicates the interpretation of serum levels; theses metabolites accumulate during chronic primidone therapy. The phenobarbital concentration reaches measurable levels in about a week and eventually equals the primidone concentration.